1. Field of the Invention
The present invention relates to a videotext receiver which receives and decodes the textual and graphic data multiplexed for transmission with a normal television broadcast for display on a CRT or other display device.
2. Description of the Prior Art
Various multiplex television broadcasting formats have been considered in recent years to more efficiently utilize existing broadcasting bands. One of these is videotext, already a commercialized broadcasting service whereby news and weather reports, stock market information, and other information comprised of text and/or graphics can be received and displayed on a home television receiver.
A typical videotext broadcast receiver currently used in the above system to receive the textual and graphic data multiplexed with the television broadcast signal and to display this information on a home television receiver is described below with reference to FIG. 6.
FIG. 6 shows the construction of a conventional videotext receiver wherein element 1 is the text and graphic data decoder 1 which restores the textual and graphic data to a text and graphic image; element 2 is a microprocessor for controlling the textual and graphic data decoder 1; element 3 is a receiver circuit for extracting the textual and graphic data from the video signal as digital data; element 4 is a RAM that stores the received textual and graphic data and is used as the operating area of the microprocessor 2; element 5 is an ROM in which is written the program controlling the operation of the microprocessor 2; element 7 is a video display memory in which is stored the text and graphic image decoded by the microprocessor 2; element 6 is a display processor that synthesizes the text and graphic image stored in the video display memory 7 into an RGB signal; element 9 is a character generator used when the textual and graphic data is decoded into a text and graphic image; element 8 is an added sound decoder used to process the additional sound data included in the textual and graphic data; and element 10 is a keypad used to select the desired text and graphic data for display.
Reference number 20 is a television signal receiver, which is comprised of an antenna 21, a television signal receiver circuit 22, an audio demodulation amplifier 23, a brightness amplifier and color demodulator circuit 24, a video/voice selector 25 which selects or mixes the video sound signal or the RGB signal and added sound signal output from the textual and graphic data decoder 1, an audio amplifier output circuit 26, a video amplifier output circuit 27, a speaker 28, and a display 29 for displaying the video image.
The operation of a conventional videotext receiver constructed as described above is described below.
The television signal input from the antenna 21 is demodulated by the television signal receiver circuit 22 in the television signal receiver 20, and video and audio signals are thereby extracted. The video signal is input to the receiver circuit 3 of the textual and graphic data decoder 1, and the text and graphic data is extracted from the video signal. When the user operates the keypad 10 to select the desired text and graphic data program from the many text and graphic data programs received, a request is sent from the keypad 10 to the microprocessor 2. The microprocessor 2 accordingly selects the requested text and graphic data program, and converts the text and graphic data to a text and graphic image according to the program written in the ROM 5 and using the character generator 9 as may be required. The resulting text and graphic image is then stored in the video display memory 7. The text and graphic image in the video display memory 7 is synthesized as an RGB signal by the display processor 6, and any additional sound data contained in the text and graphic data is converted to the added sound signal by the added sound decoder 8.
At the same time, the audio and video signals demodulated by the television signal receiver circuit 22 are respectively input to the audio demodulation amplifier 23 and the brightness amplifier and color demodulator circuit 24 where they are processed and then output to the video/voice selector 25. The video/voice selector 25 switches and selects the video signal (RGB signal) and audio signal (the added sound signal) output from the text and graphic data decoder 1 when the user selects a videotext program, or selects the television video and audio signals when the user selects a regular television broadcast, and outputs the selected signals to the speaker 28 and display 29 via the audio amplifier output circuit 26 and video amplifier output circuit 27, respectively. The user is thus able to view the selected television program or videotext program on the display 29.
During videotext program reception, there is a delay from the time the user selects the desired program to the time that program is received and displayed on the screen. To eliminate this delay, conventional videotext receivers store the videotext program in memory.
In the videotext receiver shown in FIG. 6, the program number of the text and graphic data to be stored in the RAM 4 and the channel number of the television broadcast are selected by the user by operating the keypad 10. The microprocessor 2 then stores the selected videotext program in the RAM 4.
At this time the user may also use the keypad 10 to enter a memo so that the contents of the selected program can be easily identified later.
The microprocessor 2 stores the selected program number of the text and graphic data, channel number, and memos in the RAM 4. As controlled by the user with the keypad 10, the microprocessor 2 may also display on the screen a list of the text and graphic data program numbers, channel numbers, and memos stored in the RAM 4.
The user is then able to refer to this list of program numbers, channel numbers, and memos to quickly view any selected program with no delay in the display time.
However, in a videotext receiver of this type, the user must first work the keypad 10 to enter the program numbers, channel numbers, and memos for all desired programs in order to display on screen a list of the videotext program numbers, channel numbers, and memos stored in memory, and this data entry operation is both complicated and inconvenient.